//字体大小定义
$font_size_12: 12px;
$font_size_14: 14px;
$font_size_16: 16px;
$font_size_18: 18px;
$font_size_20: 20px;
//字体调整的差量
$size: 0;
$size_4: 1px;
$size_6: 2px;
$size_8: 3px;
